Multiple air pressure actuated horn



March 28, 1950 R. E. SWANSON I MULTIPLE AIR PRESSURE ACTUATED HORN Filed March 8, 1949 0 s M w. .T TN 2 WW.

Patented Mar. 28, 1950 UNITED STATES 2,502,354 MULTIPLE AIR PRESSURE ACTUATED HORN of New York Application March 8, 1949, Serial No. 80,231

3 Claims.

My invention relates to improvements in multiple air pressure actuated horns, the object of which is primarily to so combine a number of horns for unitary operation that they will collectively have the same characteristics as the conventional steam whistle of the steam railway locomotive in accepted use throughout the North American Continent.

With the present Diesel locomotive which is becoming increasingly popular with all railway companies, the problem of providing a suitable audible warning device which could not be mistaken for the whistle of an industrial plant or a steam ship and yet provide one which would be instantly recognized as a warning of a moving train has not been previously solved. The use of a steam whistle is not possible on Diesel locomotives for the lack of steam at 200 p. s. i. or more, and air or vibrator horns have not hither- .to been developed to the point that the tone of unmistakable warning of the approach of a train.

I have discovered that to reproduce the sound of the conventional steam whistle with air horns, it is necessary to provide such a combination of horns as to produce five fundamental notes chorded to a third diminished scale with the inherent flute note harmonics superimposed on the fundamental notes of the chord.

I have also discovered that the ringing bell effect of steam whistles on ships and the like is largely due to. the bell chamber of said whistles, but is not present in locomotive steam whistles and must therefore be kept out of the horn combination herev to be described.

The invention will be morev fully described in the following specification and shown in the accompanying drawings in which:

Figure 1 is a side elevational view of the vention.

Figure 2 is a front View, showing the preferred manner of grouping the several horns or reso nators.

Figure 3 is a longitudinal fractionated sectional view taken through one of the several horns.

Figure 4 is a rear view of same.

Figure 5 is a fragmentary sectional View along the plane of line 5--5 in Figure 2.

In the drawings like characters of reference indicate corresponding parts in each figure.

The numeral l indicates generally a base having a bed plate 2 supporting a vertical member 3 on which the resonator 5 of a horn 6 is secured longitudinally, preferably by welding. Radiating from the resonator 5 are five plate members 8, shown in dotted line in Figure 2, which support horns in, II, l2, l3 and M by being secured to their resonators 5 as in the case of the horn 6. spacers I5 are interposed and secured between adjacent plate members i which serve to make the structure more rugged, but have the primary object of deadening undesirable metallic harmonics set up in the metal due to the frequency vibration of the chorded not produced.

The horns 6, [0, H, l2, l3 and M each have a resonator 5, each of which is engaged in the throat l! of a circular air chamber [8, see detail in Figure 3. Each air chamber is provided with an annular air passage is which is capped by a membrane or diaphragm 20 and each membrane is weighted as at 2| to vibrate at a predetermined frequency per second. Each membrane 20 is held in place and tensioned within its air chamber by an adjustable threaded plug 23 which is webbed on its rear face to deaden undesirable metallic harmonics which might otherwise be set up in the air chamber. The horns are made with their membranes weighted to vibrate at the following frequencies:

Membrane of horn 0 vibrates at 256 per secondwith overtone inherents 512, 1024.

Membrane of horn l0 vibrates at 304 per second with overtone inherent 608, 1216.

Membrane of horn ll vibrates at 360 per second with over-tone inherents. 720, 1440.

Membrane of horn l2 vibrates at 428 per sec-.

ond with overtone inherents 856, 1712.

Membrane of horn is vibrates at 510 per secend with overtone inherents 1020, 20.40.

Membrane of horn l4 vibrates at 608 per second with overtone inherents 1216, 2432.

It will be noticed that the membrane of horn M has the same vibration rate as the overtone inherent of the membrane of horn I0.

The resonators of horns 6, H), II, l2, l3 and M are. threaded at their inner ends as at 311 and are screwed into the throats 1 and secured in adjusted position by lock nuts 36. The provision of the adjustment enables each resonator to be tunable as to tone and also to allow for Substantially segmental retuning necessary to correct any tone defect occurring to any of said resonators through train wreck or otherwise.

There is a vibration or tremble in the locomo tive whistle which is not inherent in air horns and I have found that this can be developed in my multiple air horn by tuning in a beat to the octave of the resonator of horn 8 which enhances the tone.

The membrane of horn it is of the same note as the octave of the resonator of horn if} viz: 608 vibrations per second. This frequency and that of its overtones is found to be necessary in simulating the note of the locomotive steam whistle.

The several horns and their membranes are proportional to each other, so that when sounded with the same intensity neither the high frequencies nor the low frequencies are dominant to the human ear and all notes sounded together cause no discomfort to the human ear and sound as a single chord.

Each of the air chambers I8 is provided with an air inlet fitting 38 and pipes ii] are connected to each of said fittings from a source of air at a suitable pressure.

The multiple air horn here described employs the principle of six horns each having an adjustable resonator and a membrane, all of which membranes are vibrated by the passage of a flow of compressed air from a common source of supply and in which each membrane vibrates in sympathy with the natural frequency of its adjustable resonator. The length of each resonator varies inversel as the frequency of the note emitted by each resonator.

The development or the present invention is to provide a multiple air horn having six horns, each with a separate resonator which collectively produce a combined sound consisting of five fundamental flute notes chorded to a third diminished scale with the inherent flute note harmonics being superimposed on the fundamental notes of the chord, the flute not harmonics being thirds and sevenths with the fundamental dominant.

The frequency of vibration of each of the membranes is the result of the fourth root of two multiplied by the frequency of the next lower note, consequently while it is intended to simultaneously sound all the dominant notes of each of the horns, if one or two of said horns fail to function at any time the remaining horns will collectively sound a chord having the inherent characteristics of the locomotive whistle and its warning will be accepted as such by the individual hearing it. It might be here pointed out that the sound is not directional and can therefore be heard almost as well to the rear as to the front of the train on which it is installed.

What I claim as my invention is:

1. A multiple air horn having substantially the sound characteristics of a locomotive steam whistle which comprises at least two pairs of air horns, each of said horns being provided with a soundproducing membrane and a sound amplifying resonator associated in tuned relationship with each membrane, and damping means comprising structural elements rigidly interconnecting said resonators whereby extraneously produced harmonic vibrations originating in the resonators are damped, each of the membranes and resonators of one pair of horns being tuned to a fundamental note, the frequency of one of said notes being sufficiently close to the frequency of the next adjacent octave of the other of said notes as to produce a beat frequency therebetween, and each of the membranes and resonators of the other pair of horns being tuned to an additional fundamental note, the frequency of one of said additional notes being tuned to the octave of the frequency of the other of said additional notes, the respective membranes and resonators of the two pairs of horns being further tuned to a third diminished scale.

2. A multiple air horn having substantially the sound characteristics of a locomotive steam whistle which comprises at least five air horns, each of said horns being provided with a soundproducing membrane and a sound amplifying resonator associated in tuned relationship with each membrane, and damping means comprising structural elements rigidly interconnecting said resonators whereby extraneously produced harmonic vibrations originating in the resonators are damped, each of the membranes and resonators of two of the horns being tuned to a fundamental note, the frequency of one of said notes being sufficiently close to the frequency of the next adjacent octave of the other of said notes as to produce a beat frequency therebetween, each of the membranes and resonators of another two of the horns being tuned to an additional fundamental note, the frequency of one of said additional notes being tuned to the next adjacent octave of the frequency of the other of said additional notes, and the membrane and resonator of the fifth horn being tuned to a fifth and different fundamental note, the respective membranes and resonators of the five horns being further tuned to five fundamental notes chorded to a third diminished scale.

3. A multiple air horn having substantially the sound characteristics of a locomotive steam whistle which comprises a plurality of air horns, each of said horns being provided with a soundproducing membrane and a sound amplifying resonator associated in tuned relationship with each membrane, and damping means comprising structural elements rigidl interconnecting the resonators whereby extraneously produced harmonic vibrations originating in the resonators are damped, the horns being present in such number with their respective membranes and resonators tuned to different fundamental notes as to comprise a diminished third chord, each of the membranes and resonators of two of the horns being tuned to a fundamental note, the frequency of one of said notes of the two horns being tuned to the next adjacent octave of the frequency of the other of said notes of the two horns, and each of the membranes and resonators of two others of said plurality of horns being tuned to produce a beat frequency between said last named other two horns.

ROBERT EUGENE SWANSON.

GEES CITED- The following references are of record in the file of this patent:

UNITED STATEE PATENTS Number Name Date 1,660,785 Cooper Feb. 28, 1928 1,691,215 Sparks et a1 Nov. 13, 1928 1,691,321 White et a1 Nov. 13, 1928 1,698,804: Sparks et al Jan. 15, 1929 2,094,422 Aufiero Sept. 28, 1937 22,159,801 Kelley May 23, 1939 

